1. Field of the Invention
The present invention relates to novel olefin polymerization pre-catalysts which have exhibited the ability to polymerize a variety of xcex1-olefins in a stereospecific and living fashion when activated by a co-catalyst.
2. Background Art
It is well-known that certain aluminum alkyls such as ethylaluminum chlorides form heterogeneous olefin polymerization catalysts in combination with titanium tetrachloride, as is evident from the independent work of Ziegler and Natta. Ziegler, Angew. Chem. 67: 213 (1955); Natta et al., J. Am. Chem. Soc. 77: 1708 (1955). U.S. Pat. No. 2,827,446 to Breslow provides a modified version of those first generation catalysts wherein triethylaluminum was used as the co-catalyst in place of diethylaluminum chloride.
Typical Ziegler-Natta catalysts are all heterogeneous systems, which means that complicated surface phenomena strongly influence the catalyst performance. Many attempts have been made to explain and also to modify the performance of such so-called multiple-site catalysts.
A very early and important approach was that of Natta and Breslow in which each independently used a soluble transition metal compound/aluminum alkyl system in order to study the mechanism of Ziegler-Natta catalysis in homogeneous media. Natta, Chem. Ind 39: 1032 (1957); Breslow et al., J. Am. Chem. Soc. 79: 5073 (1957); Breslow et al., J. Am. Chem. Soc. 81: 81 (1959). It was found that the combination of diethylaluminum chloride and titanocene dichloride resulted in an ethylene polymerization catalyst. However, the activity of this catalyst was found to be much less than the heterogeneous Ziegler-Natta catalysts.
The next milestone of olefin polymerization catalysis was marked by Sinn and Kaminsky, who determined that partly hydrolyzed aluminum alkyls known as aluminoxanes are highly effective co-catalysts for metallocene-type transition metal complexes. In particular, the combination of metallocenes based on zirconium, titanium and hafnium with methyl aluminoxane (MAO) was found to yield much more active polymerization catalysts than the usual heterogeneous Ziegler-Natta catalysts in many olefin polymerization reactions. Sinn et al., Angew. Chem. 92: 39 (1980). Sita and Babcock also describe a combination of titanium amidinates with MAO that was found to yield active polymerization catalysts in the polymerization of ethylene, albeit with lower polymerization activity than with known do group 4 metal complexes. Sita et. al., Organometallics, 17: 5228 (1998).
In addition to their very high polymerization activity, the Kaminsky-Sinn metallocene/methyl aluminoxane catalysts have additional advantageous features which include: (a) access to new polymer modifications in terms of chemical, physical and mechanical properties and (b) access to new polymer structures including specific comonomer incorporation, highly stereoselective polymerization and the reduction of undesirable side-product formation.
Because of these important advantages, metallocene-based xe2x80x9csingle-sitexe2x80x9d catalysts have unleashed a technology revolution in industrial olefin polymerization as reflected in the rapidly increasing amount of literature in this field.
Despite the numerous advantages noted above, the particular application of MAO as the co-catalyst for metallocenes introduces some intractable problems with this technology. One such problem is that a considerable excess of methylaluminoxane compared to the amount of metallocene is required in order to get a satisfactory polymerization activity. Typically the transition metal/aluminum molar ratio is between 1:100 and 1:2000. Furthermore, MAO is readily soluble only in aromatic hydrocarbons, and hence these rather unfavorable solvents must be used in any homogeneous polymerization process.
A further complication in the use of MAO arises from the limited shelf-life of methyl-aluminoxane in aromatic hydrocarbons: aging can cause gel formation in such MAO solutions and thus hinder the preparation of homogeneous catalyst systems.
Because of the importance of single-site catalysts, persistent attempts have been made to overcome the MAO-related problems by modifying MAO through incorporation of higher alkyl groups (i.e. isobutyl groups) or supporting the co-catalyst on silica or other inorganic carriers.
Even if these co-catalysts modifications eventually solve most of the above-mentioned problems, other problems may arise in their turn, namely the reduced polymerization activity of MAO modified through incorporation of higher alkyl groups and the insolubility of supported MAO, which restricts its application to slurry and gas-phase processes.
Another approach has been to find a surrogate for MAO by using ionic complexes based on organoboron to convert the metallocene into an active, homogeneous olefin polymerization catalyst. See, e.g., Hlatky et al., J. Am. Chem. Soc. 111:2728-2729 (1989). The main advantage of such systems is that high polymerization activity is achieved at a stoichiometric metallocene/activator ratio of 1:1.
U.S. Pat. No. 5,912,202 discloses a method for preparing an activated catalyst composition which comprises reacting a xe2x80x9csingle sitexe2x80x9d catalyst precursor with an activating co-catalyst (e.g., [PhNMe2H][B(C6F5)4]) before, during or after reacting the single site catalyst precursor with a weakly coordinating electron donor such as 1-hexene.
In view of the disadvantages noted in the prior art polymerization catalysts, there is still need for improved, versatile, high-performance olefin polymerization catalysts. In addition, although major advances have been made during the past decade in the development of Ziegler-Natta catalysts that perform either stereospecific (See Brintzinger et al., Angew. Chem. Int. Ed. Engl. 34:1143-1170 (1995); Britovsek et al., Angew. Chem. Int. Ed. Engl. 38:428-447 (1999); Asanuma et al., Polym. Bull. 25:567-570 (1991); Coughlin and Bercaw, J. Am. Chem. Soc. 114:7606-7607 (1992); Kesti et al., J. Am. Chem. Soc. 114:9679-9680(1992); Babu et al., Macromolecules 27:3383-3388 (1994); van der Linden et al., J. Am. Chem. Soc. 117:3008-3021 (1995); Yamaguchi et al., J. Polym. Sci. A: Polym. Chem. 37:283-292 (1999); Stehling et al., Macromolecules 32:14-20 (1999)) or living polymerization (See Doi et al., Macromolecules 19:2896-2900 (1986); Scollard and McConville, J. Am. Chem. Soc. 118:10008-10009 (1996); Baumann et al., J. Am. Chem. Soc. 119:3830-3831 (1997); Killian et al., J. Am. Chem. Soc. 118:11664-11665 (1996); Hagihara et al., Macromolecules 31:3184-3188 (1998); Yasuda et al., J. Am. Chem. Soc. 114:4908-4910 (1992)) of xcex1-olefins, there is still a complete lack of highly active homogeneous catalysts that can effect both simultaneously. The present invention relates to a class of transition metal complexes that function as catalyst precursors for the living Ziegler-Natta polymerization of xcex1-olefins upon activation by a borate co-catalyst. More importantly, these transition metal complexes possess the ability to polymerize xcex1-olefins in both a stereospecific and living fashion.
The invention relates to a method for preparing an activated olefin polymerization catalyst composition, which comprises reacting an olefin polymerization pre-catalyst having the Formula (I): 
wherein the dotted lines indicate a delocalized bond;
M is Ti, Zr or Hf;
each R1 is independently hydrogen or alkyl or two adjacent R1 form an aromatic ring;
each R2, R3 and R4 is independently alkyl, cycloalkyl, Si(alkyl)3, Si(aryl)3, optionally substituted Si(aryl)3, optionally substituted phenyl, alkphenyl or optionally substituted alkphenyl; or
one R1 and one of R2, R3 and R4 together form an alkyl, aryl, arylalkyl or alkylarylalkyl bridge; and
each R5 is independently alkyl, cycloalkyl, aryl, optionally substituted aryl, arylalkyl or optionally substituted arylalkyl;
with an activating co-catalyst having the Formula:
[A+][xe2x88x92BR64] or BR63
wherein A+ is a cationic Lewis or Brxc3x8nsted acid capable of abstracting a methyl from the metal, M, of the olefin polymerization pre-catalyst;
B is the element boron; and
R6 is phenyl or optionally substituted phenyl.
The invention further relates to an activated olefin polymerization catalyst composition obtained by the method of the present invention.
The invention further relates to a method for preparing a polyolefin, comprising reacting an xcex1-olefin with the activated olefin polymerization catalyst composition of the present invention under conditions whereby the polyolefin is produced.
The invention further relates to the method for preparing a polyolefin, comprising reacting a diene with the activated olefin polymerization catalyst composition of the present invention under conditions whereby the polyolefin is produced.
The invention further relates to the method for preparing a block co-polymer, comprising reacting a combination of two or more different xcex1-olefins, two or more different dienes or two or more different aromatic compounds having vinyl unsaturation or any combination thereof, with the activated olefin polymerization catalyst composition of the present invention under conditions whereby said block co-polymer is produced. In particular, the invention relates to a method for the preparation of a block co-polymer, comprising reacting an xcex1-olefin and a non-conjugated diene with the activated olefin polymerization catalyst composition of the invention under conditions whereby said block co-polymer is produced.
The invention further relates to the method for preparing a highly isotactic polyolefin, comprising:
(a) preparing an activated olefin polymerization catalyst, which comprises reacting an olefin polymerization pre-catalyst having the Formula (I): 
wherein the dotted lines indicate a delocalized bond;
M is Zr, Ti or Hf;
each R1 is independently hydrogen or alkyl or two adjacent R1 form an aromatic ring;
each R2, R3 and R4 is independently alkyl, cycloalkyl, Si(alkyl)3, Si(aryl)3, optionally substituted Si(aryl)3, phenyl, optionally substituted phenyl, alkphenyl or optionally substituted alkphenyl; or
one R1 and one of R2, R3 and R4 together form an alkyl, aryl, arylalkyl or alkylarylalkyl bridge; and
each R5 is independently alkyl, cycloalkyl, aryl, optionally substituted aryl, arylalkyl or optionally substituted arylalkyl;
with an activating co-catalyst having the Formula:
[A+][xe2x88x92BR64] or BR63
wherein A+ is a cationic Lewis or Brxc3x8nsted acid capable of abstracting a methyl from the metal, M, of the olefin polymerization pre-catalyst;
B is the element boron; and
R6 is phenyl or an optionally substituted phenyl; and
(b) reacting an xcex1-olefin or a combination of two or more unlike xcex1-olefins with the activated olefin polymerization catalyst under conditions whereby said highly isotactic polyolefin is produced.
The invention also relates to the polyolefins, including homopolymers, co-polymers and block co-polymers, made according to the methods of the invention.
The invention also relates to an olefin polymerization pre-catalyst of the Formula (I): 
wherein the dotted lines indicate a delocalized bond;
M is Zr or Hf;
each R1 is independently hydrogen or alkyl or two adjacent R1 form an aromatic ring;
each R2, R3 and R4 is independently alkyl, cycloalkyl, phenyl, optionally substituted phenyl, alkphenyl or optionally substituted alkphenyl;
each R5 is independently alkyl, cycloalkyl, aryl, optionally substituted aryl, arylalkyl or optionally substituted arylalkyl;
with the proviso that R2 and R3 are not the same.